Laser irradiation apparatus

ABSTRACT

There are disposed two homogenizers for controlling an irradiation energy density in the longitudinal direction of a laser light transformed into a linear one which is inputtted into the surface to be irradiated. Also, there is disposed one homogenizer for controlling an irradiation energy density in a width direction of the linear laser light. According to this, the uniformity of laser annealing can be improved by the minimum number of homogenizers.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a laser light irradiation apparatuswhich has been improved in uniformity over an irradiated surface.

2. Description of the Related Art

In recent years, there is known a technique in which a crystallinesilicon film is formed on a glass substrate and a thin film transistoris formed by using the crystalline silicon film.

As a method of obtaining a crystalline silicon film, there is known atechnique in which an amorphous silicon film is first formed by a plasmaCVD method or the like, and irradiation of a laser light is carried outto the amorphous silicon film to transform it into the crystallinesilicon film.

An annealing method with this laser light irradiation is also used forannealing the source and drain regions of a thin film transistor formedin a self-aligned manner.

Although the method with the laser light irradiation is a techniquecapable of obtaining high crystallinity, there is a problem that themethod is disadvantageous for a treatment of a large area.

However, in the case where an active matrix type liquid crystal displaydevice having a large area is manufactured, there are no effectivemethods under the present situation other than the above-mentionedmethod of using the laser light.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a technique in which laserlight irradiation to a large area can be carried out with highuniformity. Also, another object of the invention is to provide atechnique in which a crystalline silicon film having a large area isobtained by using such a laser light.

Also, it is still another object of the invention to provide a techniquein which various kinds of annealing with irradiation of a laser light toa semiconductor device formed on a substrate having a large area can becarried out with high uniformity.

According to the study of the present inventors, it has been apparentthat a method described below is effective as a method of annealing asilicon film having a large area. This method is such that a laser lightis optically transformed into a linear beam having a width of severalmillimeters and a length of several tens centimeters, and theirradiation with this linear laser light is carried out while the scantherewith is carried out in the width direction thereof.

According to this method, laser light irradiation to a large area can becarried out by one scan. This method is superior in operation efficiencyand uniformity of irradiation effect to a conventional method in whichirradiation is carried out while scan to a spot with several centimeterssquare is sequentially carried out.

However, this method has a problem that the unevenness of laserirradiation density in the longitudinal direction of the linear laserbeam is apt to become remarkable.

It is supposed that this problem is caused since the laser light with awidth of several centimeters oscillated from an oscillator is opticallyenlarged into the length of several tens centimeters in the longitudinaldirection of the linear laser beam.

On the other hand, in the width direction of the linear laser beam,since the laser beam with a width of several centimeters is reduced intothe width of several millimeters, the uniformity in the width directiondoes not become a serious problem.

An apparatus for the linear laser beam irradiation is schematicallyshown in FIG. 4. FIG. 4 shows an oscillator 101 for oscillating a KrFexcimer laser light, and a lens system of lenses 102 and 103 foroptically transforming the laser light oscillated from the laseroscillator 101 into a predetermined laser beam.

Further, the laser beam from the lens system comprised of the lenses 102and 103 is inputted into homogenizers 80 and 81 for homogenizing thedistribution of energy density.

Furthermore, the laser beam from these two homogenizers 80 and 81 isinputted into a lens 106 for converging the beam in the width directionof the laser light to be finally transformed into a linear one.

Also, the laser beam is enlarged in the longitudinal direction of thelinear laser light by a lens 107. Although the figure does not show thatthe laser beam is enlarged to a large degree as compared with theoriginal laser beam, the laser beam with a dimension of severalcentimeters is actually enlarged into several tens centimeters.

Further, the laser light is reflected by a mirror 108, and is convergedby a lens 109, then the beam as the linear laser light is irradiatedonto a surface 100 to be irradiated.

In such a structure, the homogenizers 80 and 81 control the distributionof irradiation energy density of the irradiation laser beam.

The homogenizer 80 has a function to control the distribution ofirradiation energy density in the width direction of the linear laserbeam. The homogenizer 81 also has a function to control the distributionof irradiation energy density in the longitudinal direction of thelinear laser beam.

Such a structure is basically for the case where square or circularlaser beams are formed. That is, such a structure is effective for thecase where, in the final irradiation of laser beam, the components ofbeam pattern in the axial directions orthogonal to each other are notmuch different from each other. As a conventional example of such astructure, there is known a structure disclosed in U.S. Pat. No.4,733,944. The structure disclosed in this U.S. Patent is also anexample for the case where the beam pattern in the axial directionsorthogonal to each other is symmetrical.

However, when irradiation of a linear laser beam is carried out, thesectional shape of the beam in the longitudinal direction thereof isremarkably different from that of the beam in the width directionthereof. Accordingly, the state of distribution control of irradiationenergy density to be obtained becomes different between the longitudinaldirection and the width direction.

That is, the unevenness of irradiation energy density in the widthdirection of the linear laser light hardly becomes a problem because thewidth is narrow. However, the distribution of irradiation energy densityin the longitudinal direction of the linear laser light becomes aserious problem because the dimension is largely enlarged. That is,control means for the distribution of irradiation energy density shouldbe different for the respective directions.

The present invention disclosed in the present specification has beenmade on the basis of the above-described knowledge. The basic structureof the present invention is characterized in that the number ofhomogenizers for controlling the distribution of irradiation energydensity in the longitudinal direction of a linear laser light is largerthan that of homogenizers for controlling the distribution ofirradiation energy density in the width direction of the linear laserlight.

With this structure, there is obtained a laser irradiation apparatus inwhich the expensive homogenizers are effectively used to obtainnecessary uniformity of annealing.

According to a first aspect of the invention, as specific structurethereof is shown in FIG. 1, a laser irradiation apparatus forirradiating a linear laser light comprises a homogenizer 11, A=1 innumber, corresponding to the width direction of the linear laser light,and homogenizers 12 and 13, B=2 in number, corresponding to thelongitudinal direction of the linear laser light, and is characterizedby A<B.

In the above structure, the sum of A and B is an odd number.

According to another aspect of the invention, a laser irradiationapparatus for irradiating a linear laser light is characterized in thatthe number of homogenizers for controlling the irradiation energydensity in the width direction of the linear laser light is differentfrom that of homogenizers for controlling the irradiation energy densityin the longitudinal direction of the linear laser light.

According to a still another aspect of the invention, a laserirradiation apparatus for irradiating a linear laser light ischaracterized in that the total number of homogenizers is an odd number.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a laser irradiation apparatus forirradiating a laser light;

FIG. 2 is a schematic view showing a laser irradiation apparatus forirradiating a laser light;

FIGS. 3(A) to 3(F) are views showing manufacturing steps of a thin filmtransistor; and

FIG. 4 is a schematic view showing a laser irradiation apparatus forirradiating a linear laser light.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[Embodiment 1]

FIG. 1 schematically shows a laser irradiation apparatus of thisembodiment. In FIG. 1, a laser light oscillated from an oscillator 101is first transformed into a laser light having a predetermined beamshape and predetermined energy density distribution by an optical systemcomprised of a lens 102 and a lens 103.

The distribution of energy density in this laser light is corrected bythree homogenizers 11, 12, and 13.

The homogenizer 11 serves to correct the energy density of the beam inthe width direction of the laser beam which is finally transformed intoa linear one. However, since the dimension of the linear laser beam inthe width direction is about several millimeters, the role of thishomogenizer 11 is not so important.

In other words, the setting and adjustment of optical parameters of thehomogenizer 11 is not required to be so delicate.

The homogenizers 12 and 13 serve to correct the energy density of thebeam in the longitudinal direction of the laser beam which is finallytransformed into the linear one.

The laser beam is extended in the longitudinal direction by more than 10cm, the setting of optical parameters of these homogenizers 12 and 13must be carefully carried out.

Here, as shown by reference numerals 12 and 13, two homogenizers forcontrolling the distribution of the irradiation energy density in thelongitudinal direction of the laser beam are disposed to make thedistribution of the irradiation energy density in the longitudinaldirection of the laser beam more uniform.

Lenses designated by reference numerals 106, 107 and 109 serve totransform the laser beam into a linear one. That is, the lenses 106 and109 serve to narrow the laser beam in the width direction. The lens 107serves to enlarge the laser beam in the longitudinal direction inassociation with the two homogenizers 12 and 13.

In the structure shown in FIG. 1, the two homogenizers 12 and 13 controlthe irradiation energy density of the linearly transformed laser lightin the longitudinal direction.

By using the two homogenizers in this way, the distribution ofirradiation energy density in the longitudinal direction of the linearlaser light can be made more uniform. Thus, the annealing effect by thelinear laser light irradiation can be more uniformed. The number of thehomogenizers may be increased, if necessary.

In the width direction of the linear laser beam in which high uniformityis not so required, one homogenizer is disposed to obtain the requireduniformity.

[Embodiment 2]

Although this embodiment has basically the same optical system as thatshown in FIG. 1, the settings of various optical parameters are slightlydifferent.

FIG. 2 shows the structure of this embodiment. In the structure shown inFIG. 2, the positional relation between the homogenizers 12 and 13 isdifferent from that shown in FIG. 1. In this case, in accordance withthe change of the positional relation between the homogenizers 12 and13, the settings of optical parameters of the respective lenses must bechanged from the case shown in FIG. 1.

Also in the structure shown in FIG. 2, the uniformity of irradiationenergy density in the longitudinal direction of the linear laser beamcan be improved.

[Embodiment 3]

In this embodiment, there are shown steps of manufacturing a thin filmtransistor by applying the invention disclosed in the presentspecification.

A silicon oxide film or silicon oxynitride film 402 with a thickness of3000 Å as an underlying film is first formed on a glass substrate 401 bya sputtering method or plasma CVD method.

Next, an amorphous silicon film 403 with a thickness of 500 Å is formedby the plasma CVD method or a low pressure thermal CVD method. In viewof the denseness of film quality and crystallinity of a crystallinesilicon film subsequently obtained, it is preferable to use the lowpressure thermal CVD method as means for forming the amorphous siliconfilm 403.

In order to increase the annealing effect of laser light irradiation,the thickness of the amorphous silicon film 403 is preferably not largerthan 1000 Å, more preferably not larger than 500 Å. The lower limit ofthe film thickness of the amorphous silicon film 403 is about 200 Å.

Next, a metal element for promoting the crystallization of silicon isintroduced. Here, Ni is used as the metal element for promoting thecrystallization of silicon. Besides Ni, Fe, Co, Cu, Pd, Pt, Au, etc. maybe used.

Here, the Ni element is introduced by using a nickel acetate saltsolution. Specifically, the nickel acetate salt solution having apredetermined Ni concentration (here, 10 ppm in terms of weight) isdropped on the surface of the amorphous silicon film 403. In this state,a water film 404 of the nickel acetate salt solution is formed (FIG.3(A)).

Next, spin-drying is carried out by using a spin coater (not shown) toblow off a superfluous solution. Further, heat treatment at 550° C. forfour hours is carried out to obtain a crystalline silicon film 405 (FIG.3(B)).

After the crystalline silicon film 405 is formed, irradiation of a laserlight is then carried out. The crystallinity is further improved by thislaser light irradiation. This laser annealing is carried out with theirradiation of a KrF excimer laser light, which is transformed into alinear beam, while the scan of the laser light is carried out. The laserlight irradiation is carried out by using the apparatus shown in FIG. 1.That is, the apparatus irradiates the surface of the crystalline siliconfilm 405 with the linear laser light while scanning it in the widthdirection of the beam.

The crystalline silicon film 406 which has been improved in thecrystallinity is further obtained by the laser annealing shown in FIG.3(C).

Next, patterning is carried out to form a region 406 which becomes anactive layer of the thin film transistor (FIG. 3(D)).

Further, a silicon oxide film 407 functioning as a gate insulating filmand covering the active layer 406 is formed. Here, a silicon oxide filmwith a thickness of 1,000 Å as the gate insulating film 407 is formed bythe plasma CVD method.

Next, an aluminum film (not shown) with a thickness of 5,000 Å is formedto make a gate electrode. 0.1 wt.% scandium is contained in thisaluminum film in order to suppress the formation of hillocks andwhiskers in subsequent steps.

The hillocks and whiskers are needle-like or spine-like protrusionsformed by abnormal growth of aluminum.

Next, a resist mask (not shown) is disposed, and using this mask, thealuminum film (not shown) is patterned. In this way, pattern for forminga gate electrode 408 is formed. After the pattern for constituting thegate electrode 408 is formed, an anodic oxidation film is formed in thestate that the resist mask (not shown) is disposed.

Here, a solution containing 3% nitric acid is used as an electrolyticsolution. That is, in this solution, an electric current is flownbetween an anode of the pattern of the aluminum film (not shown) and acathode of platinum to form the anodic oxidation film on the exposedsurface of the pattern of the aluminum film.

The anodic oxidation film 409 formed in this step is porous. Here, sincethe resist mask (not shown) exists, this porous anodic oxidation film isformed on the side of the pattern as indicated by reference numeral 409.

The thickness of the porous anodic oxidation film is 3,000 Å. An offsetgate region can be formed by the thickness of this porous anodicoxidation film.

Next, the resist film (not shown) is removed, and anodic oxidation isagain carried out. In this step, an ethylene glycol solution containing3% tartaric acid neutralized with ammonia is used as an electrolyticsolution.

The anodic oxidation film formed in this step has a dense film quality.In this step, a dense anodic oxidation film 410 with a thickness of 500Å is formed by adjusting an applied voltage.

Since the electrolytic solution intrudes into the interior of the porousanodic oxidation film 409, there is formed the anodic oxidation film 410having the dense film quality in the state that it is brought intocontact with the gate electrode 408.

If the film thickness of the anodic oxidation film 410 having the densefilm quality is made thick, the additional thickness contributes to thesubsequent formation of the offset gate region. However, since thethickness is thin in this embodiment, the contribution to the formationof the offset gate region will be neglected.

In this way, the state shown in FIG. 3(D) is obtained. After the stateshown in FIG. 3(D) is obtained, impurity ion implantation is carried outto form source and drain regions. Here, P (phosphorus) ions areimplanted to manufacture an N-channel thin film transistor (FIG. 3(E)).

When the impurity ion implantation is carried out in the state shown inFIG. 3(E), impurity ions are implanted into regions 411 and 415. Theimpurity ions are not implanted into regions 412 and 414, which becomeregions not to be subjected to a field effect from the gate electrode408. These regions 412 and 414 function as the offset gate region.

The region designated by reference numeral 413 becomes a channel formingregion. In this way, the state shown in FIG. 3(E) is obtained.

After the above-mentioned impurity ion implantation is completed, laserlight irradiation is carried out to activate the regions where theimpurity ions are implanted. Also the laser light irradiation is carriedout by using the laser irradiation apparatus including the opticalsystem shown in FIG. 1.

After the state shown in FIG. 3(E) is obtained, an interlayer insulatingfilm 416 is formed from a silicon oxide film, silicon nitride film,silicon oxynitride film, or the lamination film thereof as an interlayerinsulating film.

Then, contact holes are formed, and a source electrode 417 and a drainelectrode 418 are formed. In this way, the thin film transistor shown inFIG. 3(F) is completed.

By applying the invention disclosed in the present specification, it ispossible to provide a technique in which irradiating a laser light withhigh uniformity onto a large area can be made. Further, annealing withhigh uniformity can be carried out to a semiconductor film having alarge area. Especially, this effect can be obtained by the minimum useof expensive homogenizers.

What is claimed is:
 1. A method of projecting laser light,comprising:oscillating a laser light; controlling an irradiation energydensity in a first direction of the laser light by using at least onefirst homogenizer; controlling the irradiation energy density in asecond direction of the laser light by using a plurality of secondhomogenizers; converging the first direction of the laser light;expanding the second direction of the laser light, wherein theconverging and the expanding change the laser light into a linear laserlight; and irradiating the linear laser light to a semiconductor filmformed on an insulating surface, wherein the number of the secondhomogenizers is larger than that of the first homogenizer, and whereinthe first direction corresponds to a width direction of the linear laserlight while the second direction corresponds to a longitudinal directionof the linear laser light.
 2. A method according to claim 1, wherein atotal number of the first homogenizer and the second homogenizers isthree.
 3. A method according to claim 1, wherein the semiconductor filmcomprises silicon.
 4. A method according to claim 1, wherein the laserlight is an excimer laser light.
 5. A method according to claim 1,wherein the first homogenizer comprises a plurality of lenses connectedin series, and wherein each of the second homogenizers comprise aplurality of lenses connected in series.
 6. A method comprising thesteps of:oscillating a laser light; controlling an irradiation energydensity in a first direction of the laser light by using a firsthomogenizer; controlling the irradiation energy density in a seconddirection of the laser light by using two second homogenizers;converging the first direction of the laser light; expanding the seconddirection of the laser light, wherein the converging and the expandingsteps change the laser light into a linear laser light; and irradiatingthe linear laser light to a semiconductor film formed over an insulatingsubstrate, wherein the first direction corresponds to a width directionof the linear laser light while the second direction corresponds to alongitudinal direction of the linear laser light.
 7. A method accordingto claim 6, wherein the semiconductor film comprises silicon.
 8. Amethod according to claim 6, wherein the laser light is an excimer laserlight.
 9. A method according to claim 6, wherein the first homogenizercomprises a plurality of lenses connected in series, and wherein each ofthe second homogenizers comprises a plurality of lenses connected inseries.
 10. A method according to claim 6, further comprising the stepsof:forming a gate insulating film adjacent to said semiconductor film;and forming a gate electrode adjacent to said gate insulating film,wherein said gate insulating film and said gate electrode are formed formanufacturing a thin film transistor.
 11. A method of processing asemiconductor comprising the steps of:forming a semiconductor film on aninsulating surface; forming a film comprising a metal element on thesemiconductor film for promoting a crystallization of the semiconductorfilm; crystallizing the semiconductor film by heating; and irradiating alinear laser light to the semiconductor film after the crystallizingstep, wherein a width direction of the linear laser light is homogenizedin an irradiation energy density by at least one first homogenizer, andwherein a longitudinal direction of the linear laser light ishomogenized in the irradiation energy density by a plurality of secondhomogenizers, the number of the second homogenizers being larger thanthat of the first homogenizer.
 12. A method according to claim 11,wherein the total number of the first homogenizer and the secondhomogenizers is three.
 13. A method according to claim 11, wherein thesemiconductor film comprises silicon.
 14. A method according to claim11, wherein the metal element is selected from a group consisting of Ni,Fe, Co, Cu, Pd, Pt and Au.
 15. A method according to claim 11, whereinthe linear laser light is an excimer laser light.
 16. A method accordingto claim 11, wherein the first homogenizer comprises a plurality oflenses connected in series, and wherein each of the second homogenizerscomprises a plurality of lenses connected in series.
 17. A methodcomprising the steps of:forming a semiconductor film on an insulatingsurface; forming a film comprising a metal element on the semiconductorfilm for promoting a crystallization of the semiconductor film;crystallizing the semiconductor film by heating; and irradiating alinear laser light to the semiconductor film after the crystallizingstep, wherein a width direction of the linear laser light is homogenizedin an irradiation energy density by a first homogenizer, and wherein alongitudinal direction of the linear laser light is homogenized in theirradiation energy density by two second homogenizers.
 18. A methodaccording to claim 17, wherein the semiconductor film comprises silicon.19. A method according to claim 17, wherein the metal element isselected from a group consisting of Ni, Fe, Co, Cu, Pd, Pt and Au.
 20. Amethod according to claim 17, wherein the linear laser light is anexcimer laser light.
 21. A method according to claim 17, wherein thefirst homogenizer comprises a plurality of lenses connected in series,and wherein each of the second homogenizers comprises a plurality oflenses connected in series.
 22. A method according to claim 17, furthercomprising the steps of:forming a gate insulating film adjacent to saidsemiconductor film; and forming a gate electrode adjacent to said gateinsulating film, wherein said gate insulating film and said gateelectrode are formed for manufacturing a thin film transistor.
 23. Amethod of processing a semiconductor, comprising the step of:irradiatinga laser light to a semiconductor film formed on an insulating surface inorder to anneal the semiconductor film, wherein a width direction of thelinear laser light is homogenized in an irradiation energy density by atleast one first homogenizer and a longitudinal direction of the linearlaser light is homogenized in the irradiation energy density by aplurality of second homogenizers, the number of the second homogenizersbeing larger than that of the first homogenizer.
 24. A method accordingto claim 23 wherein the total number of the first homogenizer and thesecond homogenizers is three.
 25. A method according to claim 23,wherein the semiconductor film comprises silicon.
 26. A method accordingto claim 23 wherein the linear laser light is an excimer laser light.27. A method according to claim 23, wherein the first homogenizercomprises a plurality of lenses connected in series, and wherein each ofthe second homogenizers comprises a plurality of lenses connected inseries.
 28. A method comprising the steps of:oscillating a laserlight:controlling an irradiation energy density in a first direction ofthe laser light by using a first homogenizer; controlling an irradiationenergy density in a second direction of the laser light by using asecond homogenizer; converging the first direction of the laser light;expanding the second direction of the laser light, wherein theconverging and the expanding steps change the laser light into a linearlaser light; and irradiating the linear laser light to a semiconductorfilm formed on an insulating surface, wherein the first directioncorresponds to a width direction of the linear laser light while thesecond direction corresponds to a longitudinal direction of the linearlaser light, and wherein the first homogenizer includes a plurality ofconvex lenses while the second homogenizer includes a plurality ofconcave lenses.
 29. A method according to claim 28, wherein thesemiconductor film comprises silicon.
 30. A method according to claim28, wherein the laser light is an excimer laser light.
 31. A methodaccording to claim 28, further comprising the steps of:forming a gateinsulating film adjacent to said semiconductor film; and forming a gateelectrode adjacent to said gate insulating film, wherein said gateinsulating film and said gate electrode are formed for manufacturing athin film transistor.
 32. A method of comprising the stepsof:oscillating a laser light; controlling an irradiation energy densityin a first direction of the laser light by using a first homogenizer;controlling an irradiation energy density in a second direction of thelaser light by using a plurality of second homogenizers; converging thefirst direction of the laser light; expanding the second direction ofthe laser light, wherein the converging and the expanding steps changethe laser light into a linear laser light; and irradiating the linearlaser light to a semiconductor film formed on an insulating surface,wherein the first direction corresponds to a width direction of thelinear laser light while the second direction corresponds to alongitudinal direction of the linear laser light, and wherein the firsthomogenizer includes a plurality of convex lenses while one of thesecond homogenizers includes a plurality of concave lenses.
 33. A methodaccording to claim 32, wherein the other one of the second homogenizersincludes a plurality of convex lenses.
 34. A method according to claim32, wherein the number of the second homogenizers is two.
 35. A methodaccording to claim 32, wherein the semiconductor film comprises silicon.36. A method according to claim 32, wherein the laser light is anexcimer laser light.
 37. A method according to claim 32, furthercomprising the steps of:forming a gate insulating film adjacent to saidsemiconductor film; and forming gate electrode adjacent to said gateinsulating film, wherein said gate insulating film and said gateelectrode are formed for manufacturing a thin film transistor.
 38. Amethod comprising the steps of:forming a semiconductor film on aninsulating surface; and irradiating a linear laser light to thesemiconductor film, wherein a width direction of the linear laser lightis homogenized in an irradiation energy density by a first homogenizerincluding a plurality of convex lenses, and wherein a longitudinaldirection of the linear laser light is homogenized in the irradiationenergy density by a second homogenizer including a plurality of concavelenses.
 39. A method according to claim 38, wherein the semiconductorfilm comprises silicon.
 40. A method according to claim 38, wherein thelinear laser light is an excimer laser light.
 41. A method according toclaim 38, further comprising the steps of:forming a gate insulating filmadjacent to said semiconductor film; and forming a gate electrodeadjacent to said gate insulating film, wherein said gate insulating filmand said gate electrode are formed for manufacturing a thin filmtransistor.
 42. A method comprising the steps of:forming a semiconductorfilm on an insulating surface; and irradiating a linear laser light tothe semiconductor film, wherein a width direction of the linear laserlight is homogenized in an irradiation energy density by a firsthomogenizer including a plurality of convex lenses, and wherein alongitudinal direction of the linear laser light is homogenized in theirradiation energy density by a plurality of second homogenizers, one ofsaid second homogenizers including a plurality of concave lenses.
 43. Amethod according to claim 42, wherein the number of the secondhomogenizers is two.
 44. A method according to claim 42, wherein theother one of the second homogenizers includes a plurality of convexlenses.
 45. A method according to claim 42, wherein the semiconductorfilm comprises silicon.
 46. A method according to claim 42, wherein thelinear laser light is an excimer laser light.
 47. A method according toclaim 42, further comprising the steps of:forming a gate insulating filmadjacent to said semiconductor film; and forming a gate electrodeadjacent to said gate insulating film, wherein said gate insulating filmand said gate electrode are formed for manufacturing a think filmtransistor.
 48. A method comprising the steps of:forming a semiconductorfilm on an insulating surface; forming a film comprising a metal elementon the semiconductor film for promoting a crystallization of thesemiconductor film; crystallizing the semiconductor film by heating; andirradiating a linear laser light to the semiconductor film after thecrystallizing step, wherein a width direction of the linear laser lightis homogenized in an irradiation energy density by a first homogenizerincluding a plurality of convex lenses, and wherein a longitudinaldirection of the linear laser light is homogenized in the irradiationenergy density by at least one second homogenizer including a pluralityof concave lenses.
 49. A method according to claim 48 wherein the numberof the second homogenizer is two, one including a plurality of concavelenses and the other one including a plurality of convex lenses.
 50. Amethod according to claim 48 wherein the semiconductor film comprisessilicon.
 51. A method according to claim 48 wherein the linear laserlight is an excimer laser light.
 52. A method according to claim 48wherein the metal is selected from the group consisting of Ni, Fe, Co,Cu, Pd, Pt and Au.
 53. A method according to claim 48, furthercomprising the steps of:forming a gate insulating film adjacent to saidsemiconductor film; and forming a gate electrode adjacent to said gateinsulating film, wherein said gate insulating film and said gateelectrode are formed for manufacturing a thin film transistor.